13.3. Linux-3.4.17

13.3.1. Installation of the kernel

La construction du noyau implique quelques étapes — la configuration, la compilation et l'installation. Lisez le fichier README dans l'arborescence des sources du noyau pour des méthodes alternatives de à celle utilisée par le livre pour configurer le noyau.

Préparez la compilation en lançant la commande suivante :

make mrproper

Ceci garantit que l'arborescence du noyau est absolument propre. L'équipe du noyau recommande que cette commande soit exécutée avant chaque compilation du noyau. Ne pensez pas que l'arborescence des sources est propre après la décompression.

Configurez le noyau avec une interface en menus. Merci de noter que le script de démarrage d'Udev exige que "rtc", "tmpfs" et "devtmpfs" soient activés et construits en dur dans le noyau et non en modules. CBLFS contient des informations sur les exigences de configuration particulières des paquets hors CLFS, sur http://cblfs.cross-lfs.org/:

make menuconfig

Sinon, make oldconfig pourrait être plus adapté à certaines situations. Voir le fichier README pour plus d'informations.

Si vous le souhaitez, passez la configuration du noyau en copiant le fichier de configuration du noyau, .config, du système hôte (s'il est disponible) dans le répertoire racine des sources déballées du noyau. Toutefois, nous ne vous recommandons pas cette option. Il vaut souvent mieux explorer tous les menus de configuration et créer de zéro la configuration du noyau.

Compilez l'image et les modules du noyau :

make

If using kernel modules, an /etc/modprobe.conf file may be needed. Information pertaining to modules and kernel configuration is located in the kernel documentation in the Documentation directory of the kernel sources tree. Also, modprobe.conf(5) may be of interest.

Be very careful when reading other documentation relating to kernel modules because it usually applies to 2.4.x kernels only. As far as we know, kernel configuration issues specific to Hotplug and Udev are not documented. The problem is that Udev will create a device node only if Hotplug or a user-written script inserts the corresponding module into the kernel, and not all modules are detectable by Hotplug. Note that statements like the one below in the /etc/modprobe.conf file do not work with Udev:

alias char-major-XXX some-module

Because of the complications with Udev and modules, we strongly recommend starting with a completely non-modular kernel configuration, especially if this is the first time using Udev.

Install the modules, if the kernel configuration uses them:

make modules_install

Installez le firmware si la configuration du noyau en utilise un :

make firmware_install

After kernel compilation is complete, additional steps are required to complete the installation. Some files need to be copied to the /boot directory.

Issue the following command to install the kernel:

cp -v vmlinux /boot/clfskernel-3.4.17

System.map is a symbol file for the kernel. It maps the function entry points of every function in the kernel API, as well as the addresses of the kernel data structures for the running kernel. Issue the following command to install the map file:

cp -v System.map /boot/System.map-3.4.17

The kernel configuration file .config produced by the make menuconfig step above contains all the configuration selections for the kernel that was just compiled. It is a good idea to keep this file for future reference:

cp -v .config /boot/config-3.4.17

It is important to note that the files in the kernel source directory are not owned by root. Whenever a package is unpacked as user root (like we do inside the final-system build environment), the files have the user and group IDs of whatever they were on the packager's computer. This is usually not a problem for any other package to be installed because the source tree is removed after the installation. However, the Linux source tree is often retained for a long time. Because of this, there is a chance that whatever user ID the packager used will be assigned to somebody on the machine. That person would then have write access to the kernel source.

If the kernel source tree is going to retained, run chown -R 0:0 on the linux-3.4.17 directory to ensure all files are owned by user root.